I once solved and animated this problem a long time ago - a pendulum with an elastic link. But I can not find this Mathcad 15 sheet. I began to create the calculation in a new way, but I do not understand where the error came from. Help me, please. See attach!
I have find the error myself!
But now an error is in the odesolve function!
Not correct but nice! A Big Apple of NYC!